1. Field of the Invention
The present invention relates to a life-saving device and, more specifically to improvement of life-saving function in a life-saving device provided with a body temperature adjuster which can adjust the temperature of the wearer.
2. Description of the Related Art
A lifesaving device (life jacket) well known in the related art is configured to ensure floating feature assuming that it is mainly used in scenes of distress. In addition, such a life-saving device is configured to be easy to wear in case of emergency and to be capable of offering buoyancy in a moment of time.
As a life-saving device as described above, for example, a vest-type inflating life-saving device is disclosed in JP-A-2002-362482. A neck-hanging style inflating life-saving device which is put around the neck is disclosed in JP-A-2002-127986. However, although such life-saving devices are configured to be inflated automatically or manually to offer buoyancy when the wearer gets into water, they are not provided with means for heating the wearer's body so as to prevent heat loss from the body when he/she is in distress in the sea area of low temperature. Therefore, in case of distress in the sea area of low temperature, there is a risk that the wearer dies before rescue corps such as a rescue boat or a rescue aircraft arrive even when such a life-saving device is putted on.
Generally, what affects the survival time of the victim in water is heat loss from the body. The temperature of human beings is automatically adjusted to keep the body temperature at 37° C. constantly. When the body temperature is decreased to 35° C. or below, he/she gets trapped into a low-temperature symptom appears, and he/she suffers from severe shakes and agony, resulting in reduction of sensitivity of nerves and confusion of consciousness. When the body temperature is further lowered below 31° C., shaking stops, but his/her muscles become stiff instead, and pulsation of heart is weakened, resulting in irregular heart pulsation. In this stage, the victim may drop into unconsciousness. It is said that when one's body temperature is decreased to 30° C. or below, one can hardly recognize whether he/she is alive or dead.
As a life-saving device corresponding to such circumstances, a life jacket provided with a radio beacon for detecting the position of distress using a GPS receiver and transmitting a position signal via a radio transmitter so as to allow rescuers arrive the site rapidly is disclosed in JP-A-2000-90377.
In addition, for example, Japanese Patent No.2696744 discloses a life jacket having a positive heating capability for extending survival time of an aircraft passenger until he/she is rescued by the rescue boat or by the rescue aircraft in the case where the aircraft has landed on the sea area of low temperature when an emergency arises.
FIG. 1 is an explanatory drawing showing the front surface of a cold-and-water-proof vest disclosed in Japanese Patent No.2696744. In this drawing, the cold-and-water-proof vest 101 includes a flat plate shaped chemical heat generating agent 102 which generates heat by oxidizing reaction in the atmosphere, a heat generating body storing bag 104 having a pocket 103 for dismountably retaining the chemical heat generating agent 102 therein and being formed of hermetical material having an closable opening, an air feed valve 106 mounted to the heat generating body storing bag 104 and capable of feeding oxygen from a compact pure oxygen tank 105 through a depressurizing regulator into the heat generating body storing bag 104, and an exhaust valve 107 mounted to the heat generating body storing bag 104 and capable of discharging air in the heat generating body storing bag 104, and is configured to feed oxygen upon operation of the air feed valve 106 to activate a heat generating action of the chemical heat generating agent 102, and to feed oxygen discontinuously by the air feed valve 106 and, if necessary, to discharge air by the operation of the air feed valve 106 and the exhaust valve 107, so that the body temperature is maintained.
However, in the life-saving device body according to JP-A-2000-90377, since the time period required for rescuers to effect a rescue is unknown, the victim has a risk to die due to heat loss from his/her body before the rescuers arrive in case of a distress in the sea area of low temperature.
In the cold-and-water-proof vest 101 disclosed in Japanese Patent No.2696744, since heating sites heated by the chemical heat generating agent 102 are mainly the wearer's chest, belly, and back, effective adjustment of body temperature cannot be achieved. Medically, heat of the body is transferred by heat conduction in the ecological tissue and circulating blood flow. The rate of heat conduction of the ecological tissue is 0.001 cal/(s·cm2·° C.) for muscle and 0.0005 cal/(s·cm2·° C.) for fat without blood flow. In contrast, the rate of heat conduction in the case where a heat quantity is transferred by blood flowing through blood vessels (100 μm in diameter), which is thicker than blood capillary (about 10 μm in diameter), at a flow rate of 1 ml/s is about 0.24 cal/(s·cm2·° C.). Therefore, in order to adjust the body temperature, it is effective to heat or cool portions of the body where thick arteries run through in the vicinity of the surface of the body. Such portions of the body include both sides of the neck where common carotid arteries run through, both armpits where axillary arteries run through, the central portion of the back of the body where aorta runs through, and both groins where external iliac arteries run through. Therefore, the cold-and-water-proof vest 101 which does not cool these portions of the body cannot control the body temperature effectively.
In addition, in the cold-and-water-proof vest 101, since the pure oxygen tank 105 which contains oxygen to be supplied to the chemical heat generating agent 102 needs to have an increased capacity for long term application, it is difficult to reduce the weight and the size.
Since the chemical heat generating agent 102 stops its heat generating action when the oxidizing action stops, the operating time is limited. Furthermore, since it is difficult to go on with fine adjustment of the temperature, concern remains about whether it is suitable as a device for supporting life. Furthermore, the chemical heat generating agent 102 generates heat upon reaction with oxygen, it is necessary to avoid contact with oxygen in the air other than when it is in use. Therefore, the chemical heat generating agent 102 is difficult to manage, and has a risk to generate heat when it is not necessary.
The cold-and-water-proof vest 101 has a heating effect, but has no cooling effect. Suppose the site of distress is the sea right on the equator, the sensible temperature may exceed 40° C. Under such situation, the body temperature may exceed a proper temperature, which may cause heat attack. Therefore, a life-saving device provided not only with a heating effect, but also with a cooling effect has been desired by people involved in aircraft or marine affairs.
Furthermore, since the cold-and-water-proof vest 101 does not have means for signaling the position of the wearer, it is difficult for rescuers to find the victim. Actually, even when the victim is wearing the life-saving device, it is difficult to get out of trouble by his/her own ability, and thus the victim cannot guard his/her own life unless he/she is rescued by the rescuers performing rescue activities. Therefore, since the cold-and-water-proof vest 101 is not configured to allow the rescuers to arrive at the site of distress as soon as possible and find quickly the victim, the victim has a risk to loose the bodily strength and hence die before being rescued.
Not only in the aforementioned marine life-saving device, but also in cloths which is designed to wear in the area where the difference between the proper body temperature and the outside temperature is significant, such cold districts or high-temperature districts, for example, warm cloths for mountains, fireman's cloths, or bullet-proof vests to be worn in battlefields such as desert regions, a cloth having a function to heat or cool the wearer's body according to the outside temperature or the body temperature has been desired.